Abstract. This paper develops techniques for empirically analyzing demand and supply in differentiated product markets and then applies these techniques to the U.S. automobile industry. Our framework enables one to obtain estimates of demand and cost parameters for a class of oligopolistic differentiated products markets. These estimates can be obtained using only widely available product-level and aggregate consumer-level data, and they are consistent with a structural model of equilibrium in an oligopolistic industry. Applying these techniques, we obtain parameters for essentially all autos sold over a twenty year period.